Frozen leg operation of a three-phase dual active bridge DC/DC converter at light loads

A three-phase dual active bridge (DAB) converter is designed and constructed as the DC/DC stage of a 50 kW fast charger station. Recently introduced 300A SiC power modules and drivers are utilized in the converter to obtain a high efficiency. Each module has two interconnected switches with anti-parallel diodes resembling a converter leg. It is observed that the driver halts the module operation as a result of protective actions such as over-current, gate under-voltage, or gate over voltage. In such case the module operates as a leg with two diodes until an external hardware signal resets the driver. The aim of this paper is to provide analysis, simulation and experiments for a three-phase DAB converter after a frozen leg condition in the secondary side of the converter and at light loads. The results show that this fault mode is non-destructive and it is possible to continue the operation by adjusting the controller and over-sizing the semiconductors.